I’m looking forward to giving an invited presentation to Butterfly Conservation South Australia (BCSA) next month. The BCSA formed over 20 years ago to promote the conservation of butterflies and moths, and their habitat. Their members hold monthly meetings which begin with a “Butterfly of the Month” presentation, before an invited lecture from a diverse range of scientists (that’s where I come in).
I’ll be talking about one of my absolute favourite topics “Brain evolution of fossil fish and the first tetrapods“. I’ll summarise some of my previous work looking at brains of lungfishes, before moving on to more recent work on other groups more closely related to tetrapods (the first terrestrial vertebrates). There’ll be some spectacular fossils to be celebrated and I’m sure to say the work ‘endocast’ at least 100 times.
I always really enjoy the opportunity to talk about my research with the public so I’m very much looking forward to the night (even though we wont get to meet face-to-face due to current social distancing guidelines). However, if you ever need somewhere to learn about, identify, attract or breed butterflies, then apparently BCSA is the place to go!
Let me tell you about my favourite fossil lungfish.
Rhinodipterus is a long-snouted, tooth-plated lungfish known from the Mid-Late Devonian Period (roughly 390-360 million years ago). There were a handful of species of Rhinodipterus known from throughout Europe described during the mid 20th Century. However, a new specimen unearthed in 2008 from the Gogo Formation in Australia sparked my involvement and interest in this lungfish.
The Gogo Formation is particularly rich in lungfish fossils and this new find represented the 11th described species from this one locality. Most equivalent deposits may have just one or sometimes two species present, but clearly the lungfish were very diverse on the ancient Gogo reef! And interestingly, this European genus (Rhinodipterus) had for the first time appeared in a different part of the world, all the way over in Australia. This is something we refer to as ‘palaeobiogeographic distribution’. I named the new species Rhinodipterus kimberleyensis, to reflect the location where this fossil was found (the Kimberley region of northern Western Australia).
Tim Sendon, who scanned the specimen at the ANU CT Lab.
Aside from being a new species, the most interesting thing about Rhinodipterus are certain features of its skeleton that are missing from other lungfish at Gogo. Rhinodipterus has cranial ribs which suggests it may have been able to breathe air! Cranial ribs are mobilized during the air gulping action in living lungfish and so their presence (as well as a suite of other features) are used to infer this ability in fossil forms. While we know all living lungfish can breathe air, it is finds such as these that help us pinpoint when this feature first evolved in the fossil lineage.
Furthermore, the specimen of Rhinodipterus that I described was so well preserved and uncrushed, it contained a near complete part of the skull called the braincase. As it’s name suggests, the braincase houses the brain inside the skull. Most lungfish fossils younger than the Devonian become more cartilaginous and don’t tend to fossilise particularly well (unlike bone, which is a harder and more durable material), so this is one of the most advanced fossil lungfish braincases known. Via CT-scanning and computer 3D-modelling I was able to create a virtual ‘endocast’ (mould of the internal cavity) of the braincase. These endocasts can give a lot of information about the early brain evolution in this most wonderful group of fishes (I’m not biased at all!) and help us to reconstruct brain morphology in extinct animals.
A virtual cranial endocast of Rhinodipterus kimberleyensis in right lateral view.
As you can see, this single specimen of Rhinodipterus has been very valuable to my research over the years so I thought the least I could do was commemorate it with a blog post. Thank you, Rhino!
Dr Alice Clement 